walter, Just my 2 cents. but the amount of work you are talking about will be alot more than a couple of hours at a machine shop. I bought my plates and had them drilled and tapped at a machine shop. I didn't even surface them like you suggest because I bought aluminum tooling plate which is already flat.
About 22 hours total at $40 per hour = $880. I got a deal because the owner is a friend of mine. Otherwise the shop rate would have been $75 per hour.
Included in this time was time to turn down the ends of 3 ball screws, drilling and squaring up of the bearing bocks for 3 screws (6 parts), holders for 3 stepper motors, and my router motor holders.
This is all for a small 12" x 12" machine. There's alot more work to a 3' x 6' table.
Another cost I incurred was time to program all this on a CNC HAAS. I might build a few more CNC routers and wanted to have them ready to go when needed.